The present invention relates generally to orientation sensors, and more specifically to gravity-based orientation sensors.
Orientation sensors are used in many applications. When orientation in two or three dimensions is required by an apparatus, orientation sensors are used. For example, computer peripheral equipment with non-traditional use parameters, including virtual reality apparatuses, wireless mice, non-pad using mice, and the like may all have and use orientation sensors.
Currently, there are many orientation sensors that are truly no more than level sensors. Often, such sensors use an air bubble in some sort of fluid to determine whether an object is level with respect to gravity. One example of such a sensor is a level or carpenter level. A carpenter level indicates only whether the object on which it is placed is level, but does not indicate the angle of inclination. Further, a carpenter level only indicates level with respect to one degree of freedom.
Various apparatuses having chambers and movable drops of mercury have been employed to determine orientation. Such apparatuses, for example that shown in U.S. Pat. No. 5,701,900, include two intersecting toroidal chambers orthogonal disposed, the chambers used to determine orientation of the apparatus. In a first embodiment, discrete electrodes are used to determine the position of the drop of mercury. In a second embodiment, reflective properties of the drop of mercury are used to determine position of the drop within a chamber. The second embodiment requires a light transmissive chamber and a source of light. The first embodiment is subject to error since the discrete electrodes only allow for discrete position determination within the chamber.
Therefore, there is a need in the art for an orientation sensor having multiple degrees of freedom, and also having a less discrete measurement parameter.
The present invention overcomes the problems of the prior art by providing an orientation sensor which provides orientation information in a gravimetric apparatus. In one embodiment, a freely movable drop of a conductive fluid moves gravimetrically within a chamber, bridging a gap between a first conductive ring and a second variable resistance member. The conductive fluid completes a circuit of a specific resistance, the specific resistance uniquely identifying the position of the conductive fluid in the chamber.
In one embodiment, the chamber measures changes in orientation in a single degree of freedom. In another embodiment, the variable resistance member extends in more than one direction so that the position of the conductive fluid in the chamber has more than one degree of freedom. In still another embodiment, the outer conductive member is a sphere, and traces are run along the inner surface of the sphere, the traces being separated by substantially the same distance for their entire length. The traces are routed along the interior of the sphere, substantially covering the entire interior surface of the sphere. A conductive ball or member, such as a metal bearing or the like, is free to move about the interior of the sphere. The bearing will come to rest covering two traces, creating a circuit therebetween. The resistance of this circuit will uniquely identify the position of the bearing within the sphere, allowing for full three-dimensional orientation sensing of the orientation of the sphere.
A method embodiment for determining the orientation of an apparatus embodiment of the present invention includes determining the position of a freely movable conductive member in an object, measuring the resistance between two contacts bridged by the conductive member, comparing the measured resistance to known resistance tables, and determining the orientation of the object from the position of the conductive member.
Other embodiments are described and claimed.